Examples of the floodgate driven by the hydraulic cylinder include a tilting gate apparatus constructed crossing a river. Such a tilting gate apparatus is used for effective use of water resources of the river by controlling the degree of tilting of the tilting gate provided crossing the river. Further, such an apparatus is used for preventing mixing of seawater with fresh water when provided at an estuary, and used for tide prevention when provided at a shore. Meanwhile, examples of the factory facility include various hydraulic devices used in a machining center.
In the tilting gate apparatus for effective use of water resources, piers are provided on both sides of the tilting gate provided crossing the river, and in each of the piers, there are provided a shaft secured to the tilting gate, and a cam secured to the shaft and rotated by the hydraulic cylinder. The degree of tilting of the gate is controlled through the shaft coupled to the cam provided in each pier and rotated by the hydraulic cylinder. Meanwhile, examples of the machining center include a hydraulic clamper for clamping a workpiece.
A circuit for driving the reciprocating hydraulic cylinder used for operating the tilting gate is divided by the hydraulic cylinder, and merely the amount of hydraulic oil needed for operating the hydraulic cylinder (the amount corresponding to the capacity of the hydraulic cylinder) travels back and forth in the circuit. Therefore, the hydraulic oil in the circuit and in the hydraulic cylinder does not circulate. Accordingly, longtime use may cause contamination of the hydraulic oil with a contaminant such as a piece of a sealing member broken by a diesel explosion caused by adiabatic compression, in the hydraulic cylinder, of a dust having entered into the circuit or the hydraulic cylinder, or of air having entered from a sealed portion of the hydraulic cylinder. As well, the hydraulic motor of the factory facility has a problem that a contamination of hydraulic oil caused by damage to a sealing member or by metal powder produced by friction between a rotating portion of the hydraulic motor and a body of the motor causes a malfunction in a control device such as a control valve and a speed adjustment valve.
The control device in which a malfunction occurs due to the contaminated hydraulic oil needs to be disassembled and cleaned to eliminate the cause of the malfunction, in order to properly control the hydraulic cylinder. Generally, before a malfunction occurs, such a control device needs maintenance and inspection to prevent the malfunction. Further, if a malfunction occurs in the hydraulic device such as the hydraulic cylinder and the hydraulic motor due to the above-described contamination, the malfunction has to be resolved, and to prevent the malfunction, maintenance and inspection are needed. Conventionally, for a hydraulic circuit, a configuration shown in FIG. 9 has been widely known as a circuit for repair, inspection, maintenance, disassembly and cleaning, or regular checking on such a control device.
The hydraulic circuit of Non Patent Literature 1 shown in FIG. 9 is the circuit for the hydraulic cylinder; however, the circuit may be used for a hydraulic motor. Therefore, in the following description, the hydraulic cylinder represents the hydraulic devices. In the hydraulic circuit shown in FIG. 9, a pile-up type stack valve 80 constituted by a lower stack valve 87 and an upper stack valve 88 is coupled to a hydraulic power supplier 10 and a hydraulic cylinder 61. The lower stack valve 87 includes a maintenance valve unit 81 and a maintenance valve unit 86, while the upper stack valve 88 includes a speed adjustment valve unit 82, a load check valve unit 84, and a solenoid switching valve unit 85.
Hydraulic pressure oil discharged from a hydraulic pump 11 of the hydraulic power supplier 10 in the above circuit passes through a manifold 89, the maintenance valve unit 86 of the lower stack valve 87, stop valves 81a and 81b of the maintenance valve 81, and the speed adjustment valve unit 82 of the upper stack valve 88, and then reaches a solenoid switching valve 85a of the solenoid switching valve unit 85. The direction of the flow of the hydraulic oil to/from a hydraulic device 60 is switched using the solenoid switching valve 85a. The hydraulic oil is supplied to/discharged from the hydraulic cylinder 61 of the hydraulic device 60 through speed adjustment valves 82a and 82b of the speed adjustment valve unit 82 and stop valves 86a and 86b of the maintenance valve unit 86.
In the above structure, the hydraulic oil from the hydraulic power supplier 10 is supplied/discharged so that a rod 65 of the hydraulic cylinder 61 moves from one position toward the other position, through operation on the solenoid switching valve 85a of the solenoid switching valve unit 85.
In the conventional art having the above structure and functions, when trouble occurs in any of the valves included in the upper stack valve 88 where delicate control devices of the pile-up type stack valve 80 are collectively disposed, or when inspection and maintenance are needed, the stop valves 81a and 81b of the maintenance valve 81 and the stop valves 86a and 86b of the maintenance valve 86 are closed thereby to close the communication between the hydraulic power supplier 10 and the hydraulic device 60; and then the upper stack valve 88 of the pile-up type stack valve 80 is detached, to perform repair, inspection, and/or maintenance.